Abrasive disc and method of making it

ABSTRACT

A reinforced abrasive disc and method for making it wherein the reinforcing member is placed at the junction between the usable and nonusable layers of abrasive material, the reinforcing member being independent and spaced apart from the anchor nuts embedded in the nonusable layer of abrasive material which are used to secure the disc to a rotatable support wheel.

O United States Patent [1113,576,090

[72] Inventor Frank 0. Shoemaker 2,279,278 4/1942 Shue 51/209 Palos Park, 111. 2,624,986 1/1953 Loofboro 51/209 [21] Appl. No. 671,309 2,926,469 3/1960 Kubsh 51/209 [22] Filed Sept. 28, 1967 3,250,045 5/1966 Caserta 51/209 [45] Patented Apr. 27, 1971 V FOREIGN PATENTS [731 Asslgnee Bendix 388,034 2/1933 Great Britain 51/209 Primary Examiner-Donald G. Kelly [54] ABRASIVE DISC AND METHOD OF MAKING IT Attorneys-Eugene C. Goodale and Plante, Hartz, Smith and 5 Claims, 3 Drawing Figs. Thompson [52] US. Cl. 51/209, 51/297 [51] Int. Cl 824d 7/04,

824d 11/00 C04) 31/16 ABSTRACT: A reinforced abrasive disc and method for [50] Field ofSear-ch ..5l/209,206 making it wherein the i f i member i placed at the (5R), 297 8 307 9 junction between the usable and nonusable layers of abrasive material, the reinforcing member being independent and [56] References CM spaced apart from the anchor nuts embedded in the nonusable UNHED STATES PATENTS layer of abrasive material which are used to secure the disc to 1,812,076 6/ 1931 Beebe 5 1/209 a rotatable support wheel.

PATENTEU mam 357E090 VI SHOEMAKER I FRANK O.

HIS ATTORNEY ABRASIVE DISC AND METHOD OF MAKING IT FIELD OF THE INVENTION The invention relates to grinding wheels of the type in which a flat disc of the abrasive material is secured to a rotatable supporting wheel, and more particularly to reinforced abrasive discs of the nut-inserted type and a method for making.

DESCRIPTION OF THE PRIOR ART Abrasive grinding wheels have been provided with reinforcing members embedded therein to increase the tensile strength and to resist the tendency to rupture under centrifugal force. With face grinding wheels it is also customary to embed securing nuts in the abrasive material which form the anchors engaged by the clamping bolts for securing the abrasive disc to a backing plate. Abrasive discs of the nut-inserted type have been difiicult to reinforce, since layers of any reinforcing material in the usable portion of the disc will change the grinding action of the disc as the reinforcing elements are encountered through normal wear.

One prior approach has been to place the reinforcing material on the backside of the disc, next to the supporting wheel. In this area, it does not interfere with the grinding action, but is in the least effective location.

Another approach has been to place the reinforcing material at the junction of the usable abrasive and the nonusable abrasive layer which contains the inserted nuts. First attempts at placing the reinforcing material in this location resulted in a warping or parting of the disc through the reinforcing section. In this location, when the disc is pressed into shape and subsequently cured, the internal reinforcement is bent out of its normal plane and thus placed under stress which ultimately results, by reason of internal resiliance and memory in the reinforcing material, in either warping or cracking the abrasive disc, The bending of the reinforcing member out of its normal plane occurs over the inserted nuts during the pressing operation.

Another approach has been to secure the. abrasive disc to the supporting wheel by means of screws inserted through the reinforcing member and embedded into the abrasive, but the clamping pressure against the reinforcing material or the abrasive sets up stresses that tend to weaken the disc.

It can be seen that one of the major problems in abrasive disc reinforcing is to place the reinforcing material at the junction of the usable and nonusable layers of abrasive material while eliminating the problems of cracking or warping of the disc due to distortion of the reinforcing material.

SUMMARY OF THE INVENTION The present invention presents an improved reinforced abrasive disc having a reduced tendency to warp and crack due to internal stresses placed on the reinforcing member during the pressing steps. The reinforcing member is embedded in the disc at the junction between the usable and nonusable layers of the abrasive disc and is entirely independent of the anchor nuts located in the nonusable layer of the disc. The pressing operation will not cause a flexing or distortion of the reinforcing material over the inserted nuts.

Thus it is an object of this invention to provide a method for placing a reinforcing member at the junction of the usable and nonusable layers of abrasive material in such manner that it will accommodate itself to the molding pressure and subsequent curing without distortion out of its normal plane.

A further object of this invention is to provide a reinforced abrasive disc in which the reinforcing material is independent of the anchor nuts.

DESCRIPTION OF THE DRAWING In the illustrative embodiment shown: FIG. 1 is a section through the abrasive disc and the support wheel to which it is to be attached,

FIG. 2 is a fragmentary perspective view of the abrasive disc with parts broken away, and

FIG. 3 is a partial section view of the disc and supporting plate in engagement.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrative embodiment shown in FIG. 1, a reinforced abrasive disc is shown generally at 2 having a usable layer of abrasive material 4 and a nonusable layer of abrasive material 6. It should be noted that the nonusable layer 6 need not be an abrasive mixture but may be of any suitable material which will perform the required function and can be bonded with abrasive layer 4. Attaching elements such as anchor nuts 8 and washers 10 are embedded in the nonusable layer of abrasive. Although a flat-type washer is shown, other types such as tapered cup washers have been successfully used. Abrasive disc 2 is clamped to a supporting wheel 12 through the use of bolts 14 which engage nuts 8.

Reinforcing member 16 is embedded in the abrasive disc at the junction between the usable layer 4' and nonusable layer 6 of the abrasive material. The reinforcing member is independent of nuts 8 and is not attached thereto.

The reinforcing member 16 may be an open wire mesh or other equivalent, as for instance a fiber glass mesh. In the illustrative embodiment shown in FIG. 2 an open wire mesh material is embedded in the abrasive disc and makes a strong reinforcement by providing many interlocking surfaces for holding the abrasive body in place. There will generally be a fine layer of material separating the upper surface of the anchor nut and the reinforcing member.

In a known manner, nuts 8 and washers 10 are attached in a predetermined arrangement upon a molding plate (not shown) upon which the abrasive disc is to be formed. A first layer of abrasive material is added to the molding plate. This material completely surrounds and extends above the upper surface of nut 8. The reinforcing material is next placed upon the surface of the first layer of abrasive material. A press plate (not shown) engages the reinforcing member and presses the first layer of abrasive material to a desired formulated density which forms the nonusable layer of the disc. The reinforcing member is not distorted out of its original plane in this operation since it is uniformly acted on by the press plate. This first compressing step presses the reinforcing and nonusable abrasive mix far enough so that no distortion of the reinforcing material takes place with the subsequent pressing of the usable portion of the abrasive. Then density of the nonusable layer 6 of the disc is at least equal to or greater than the formulated density of the usable layer 4, thus preventing distortion of the nonusable layer 6 on subsequent pressing operations. A second layer of abrasive material comprising the usable portion of the disc is then added over the reinforcing member to a desired depth, and pressed with the press plate to a desired density. Because the reinforcing member 16 is not secured to nuts 8, it is free to locate itself in the abrasive material without distortion during the pressing operation.

The abrasive disc thus formed is hardened by curing in any known or suitable operation.

As a consequence, the abrasive disc has a reinforcing member placed at the junction of the usable and nonusable layers of abrasive material which is free from internal stress and not likely to warp or crack the disc.

It will, therefore, be appreciated that the anchor nuts 8 are independent of and lie wholly below the reinforcing member 16 and hence they cannot transmit any clamping stress to the reinforcing or wire mesh.

It will be observed that the abrasive body may be worn away down to the reinforcing member since there are no obstructive members or securing devices above the reinforcing member which can interfere with the grinding operation. This gives a maximum use of the abrasive for a given thickness of the usable layer 4.

While the preferred form of the invention and mode of production has been illustrated and described by way of example, the scope of the invention is believed to be subject to minor changes and variations in material, proportions, and minor details of manufacture without departing from the scope of the invention as defined in the following claims.

lclaim:

l. A reinforced abrasive disc adapted to be attached to a rotatable supporting wheel comprising,

a first layer of material,

a second layer of abrasive material,

attachment means embedded solely in said first layer adapted to attach said abrasive disc to a supporting wheel, and

an unstressed reinforcing member at the junction of said first and second layers of material.

2. A reinforcing abrasive disc as claimed in claim 1 in which said attachment means are also independent of said reinforcing member.

3. The method of claim 6 in which said first layer is fonned by:

placing a plurality of anchor means in a predetermined arrangement on a molding plate,

spreading a layer of material around and above said anchor means,

placing a reinforcing member over said layer of material,

compressing said layer of material to a formulated density with a pressure plate acting against said reinforcing member whereby said reinforcing member is directly supported by said pressure plate during such compression and is thus protected against distortion.

4. The reinforcing abrasive disc of claim 1 in which said first layer is a nonusable layer having a greater density than that of said second layer.

5. A method of making a reinforced abrasive disc comprising the steps of;

forming a first layer of material having a plurality of attachment means embedded therein, and having an unstressed reinforcing member attached to one side thereof;

joining a second layer of abrasive material to said reinforcing member and said first layer by:

adding a layer of abrasive material over said reinforcing member;

compressing said added layer of abrasive material to a density no greater than the density of said first layer so that said reinforcing member is not distorted during said joining step; and

curing said reinforced abrasive disc. 

1. A reinforced abrasive disc adapted to be attached to a rotatable supporting wheel comprising, a first layer of material, a second layer of abrasive material, attachment means embedded solely in said first layer adapted to attach said abrasive disc to a supporting wheel, and an unstressed reinforcing member at the junction of said first and second layers of material.
 2. A reinforcing abrasive disc as claimed in claim 1 in which said attachment means are also independent of said reinforcing member.
 3. The method of claim 6 in which said first layer is formed by: placing a plurality of anchor means in a predetermined arrangement on a molding plate, spreading a layer of material around and above said anchor means, placing a reinforcing member over said layer of material, compressing said layer of material to a formulated density with a pressure plate acting against said reinforcing member whereby said reinforcing member is directly supported by said pressure plate during such compression and is thus protected against distortion.
 4. The reinforcing abrasive disc of claim 1 in which said first layer is a nonusable layer having a greater density than that of said second layer.
 5. A method of making a reinforced abrasive disc comprising the steps of; forming a first layer of material having a plurality of attachment means embedded therein, and having an unstressed reinforcing member attached to one side thereof; joining a second layer of abrasive material to said reinforcing member and said first layer by: adding a layer of abrasive material over said reinforcing member; compressing said added layer of abrasive material to a density no greater than the density of said first layer so that said reinforcing member is not distorted during said joining step; and curing said reinforced abrasive disc. 